4 inch stroker cam size question

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hemichuck

hemichuck

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I have a 408 short block that I've had built for a while with a forged 4 inch crank, eagle rods, and Icon 4.03 bore flat tops with valve notches with zero deck. I have a set of Edelbrock aluminum heads and a Holley strip dominator intake. I know that the stroker motors can run a lot more cam than a standard stroke small block and I was wondering if anyone had some guidelines to go buy when I am deciding on the cam lift/duration/etc. This engine is going in a 1970 Dart Swinger with 4 speed trans. The car is an original air conditioning and power steering, power disc brake car and I plan to retain all of these options. I will be running 3.23 gears and plan on driving the car a lot. I would like to know what the current thought is on choosing a cam for this application.
 
since your keeping all the accessories and the 3.23. i would go somewhere in the 500 lift and 232 to 238 @.050 range, with a 112 lsa. also would dump the SD and go with a LD340 or RPM air gap. As a side note if it was more on the performance side i would say 575 to 625 lift with a mid 250 to 260's at .050 on a 108lsa
 
Great choice!!! Prefer the air gap,out of the box.... Some more gear, that Strip Dominator goes to work...
 
What's your calculated static compression? Zero deck, flat tops, and the Eddy chambers could end up pretty steep, especially on pump gas. Your cam choice may be dependent on where it actually ends up.
 
I've had a stroker in my Dart since 2003. It's a heavy car with air and has 2.94s for high speed driving. I also have heavily ported edelbrocks. I started off using a bullet solid roller 255/263 and 630 lift and a strip dominator. This combo was terrible even with 11:1. Never ran right. About 6 yrs ago I had Scott Brown make me a hyd roller. Spec'd out at 230/243 and approx 560 lift (I forget now) on a 113. The manners are excellent and it has more power than the solid roller did.
 
I think the pistons are a potential issue. You'll have to pay attention to the camshaft details like Old and GM mentioned and be attentive to the timing curve if you want to run pump gas. I'd be looking at something around 230°-240° @ .050 for a hydraulic, add 3-4° for something solid.

GM- Glad to see you Pete!
 
What size tire on the back? I agree with not a lot of cam. The increased inches will make mounds of torque. And as crazy as this sounds, I'd run a TQ on the Strip Dominator with small tries. The small primary will be easier to drive on.

What head gasket and the amount of piston valve relief in cc's?
Your ratio could be as high as 12-1.
 
The compression should be in the 10.5 to 10.7 range but I could use some thicker gaskets to drop it down a little. With the aluminum heads it should be fine. It will be mainly a cruiser, I wont be doing a bunch of racing or anything. I just want it to be a nice tourqey motor that will pull a couple of old fat guys down the road at a respectable clip and spin the tires when I feel the need. I'm old enough now that comfort and ride trumps beating everybody from light to light. I have a Performer RPM air gap and an Offy Port-O-Sonic. Both of those are great intakes on the street and I am running a stick which is a little more forgiving. I have a Competition cams Hydraulic that is in the 525 lift range and I would have to look at it to see what the duration is. I will check the specs later and get back on here.
 
Depending on how much valve relief you have (I used 8cc), a zero deck 408 with Edelbrock RPMs are actually going to be over 11:1, assuming an .039"x4.1" head gasket, and 65cc combustion chambers (as advertised). With the above numbers, you'd need about an ~.060"x4.1" gasket to drop down to ~10.5:1 range...pretty good bit of squeeze there...

Please correct my numbers if they're off based on your build.
 
I didn't forget the tire size, I just don't know what I'm going to use yet. Still looking at wheels and tires. I think the calculations on comp. ratio sound about right. I will have to look at the specs on my pistons and see what the valve reliefs volumes are. I looked at the Comp cam that I had and its a 305H, 525 lift but the duration is 305 so its a little much for AC and power brakes.
 
305 is the advertise duration.

looks like 253 @ .050
 
I will have to look at the specs on my pistons and see what the valve reliefs volumes are
Click to expand...

I may've been a little generous on the valve relief volume...KB says they're only 5cc, which would kick up the compression some more. I think what I came up with yesterday was somewhere ~11.3:1
 
To directly answer the op question, we might need to know how much compression does this motor have.

Though if you were to tailor the compression to the cam, backwards, and consider the gearing...
A cam in the low/mid 240's @.050 with 278-282 duration on a 110 lobe with lift around 520-.530
 
TX, valve reliefs will drop the ratio.
 
I get that, what I'm saying is that I assumed 8cc for the reliefs and that was the figure I used for initial calculation...then I looked at KB's website and according to them, the Icon 408 flat tops only have a 5cc relief. 3cc isn't much, but it would definitely cause an increase compared to my first calculation using an assumed 8cc

EDIT: I just re-ran the numbers in my preferred compression calculator

Bore 4.030
stroke 4
head gasket .039"x4.1"
deck clearance 0"
skirt clearance 0.003"
Distance to top ring 0.31" (very arbitrary number, but a reasonable assumption)
valve relief 5cc
combustion chamber 65cc (as advertised by Edelbrock)

CR = 11.6:1
 
I originally built this motor with a 5.9 Magnum block(don't ask what I was even thinking) with the zero deck and the biggest magnum head style combustion chamber we were at about 12.5 to 13 to 1 on compression. Probably would have been a BMF in a drag car, but I wasn't building a drag car. My buddy runs a machine shop and he's in the process of machining a 1971 360 block for me right now so I can swap my rotating assembly into it. Maybe we can back off the zero deck enough to drop the compression to a usable level.
 
hemichuck said:
I originally built this motor with a 5.9 Magnum block(don't ask what I was even thinking) with the zero deck and the biggest magnum head style combustion chamber we were at about 12.5 to 13 to 1 on compression. Probably would have been a BMF in a drag car, but I wasn't building a drag car. My buddy runs a machine shop and he's in the process of machining a 1971 360 block for me right now so I can swap my rotating assembly into it. Maybe we can back off the zero deck enough to drop the compression to a usable level.
Click to expand...

12.5 to 13 sound more like it. Same flat top icon pistons,4" stroke on a 74 360 block that i had decked to have "0" deck and 62 cc heads came out to 12.22:1

Have you considered having the pistons dished to lower compression. instead of a hole new block?

I would call icon and see how much you could safely take off.... it's another avenue to search out.

In fact, wouldn't it be cheaper to just buy a set of dished icon piston and call it good?
 
hemichuck said:
I originally built this motor with a 5.9 Magnum block(don't ask what I was even thinking) with the zero deck and the biggest magnum head style combustion chamber we were at about 12.5 to 13 to 1 on compression. Probably would have been a BMF in a drag car, but I wasn't building a drag car. My buddy runs a machine shop and he's in the process of machining a 1971 360 block for me right now so I can swap my rotating assembly into it. Maybe we can back off the zero deck enough to drop the compression to a usable level.
Click to expand...

IIRC,the decks are indeed taller on a untouched LA block,to a untouched Magnum block. My .02....
 
As others are saying, too much compression. IMO you should swap the flat tops for some dished units. Shoot for around 9.5 compression. You could probably sell the flat tops to someone with a racier motor. I'd think a hydraulic cam in the 245-250 @ .050 ground on a 110-112 LSA would work well for you.
 
Icon does make another 408 piston-I want to say they have like a 23cc dish, which with the same numbers I used above would bring it down to 9.9~9.8:1
 
Above two posts,damn close. My KB 356's were 22+,once done.A Comp 294s solid,idled like a champ.850 in drive,slight lope... A roller,would make it smoother....
 
I have to change blocks anyway because my LA style Edelbrock heads wont oil on the Magnum block. Not really a big deal because I already have a set of Keith black stroker pistons for a magnum block(big dish) and a 4 inch Mopar Performance crank to put back in the magnum block.
 
I actually like the SRP dished - they have the smallest dishes I think at 16.5ccs.
 
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